Analyzing the limitations set by climatic factors, genotype, water and nitrogen availability on productivity of wheat. I. The model description, parametrization and validation

Abstract

A mechanistic crop growth simulation model, WTGROWS, is developed for use in analyzing effects of climatic variables and crop management on productivity of wheat in tropical and sub-tropical wheat regions of India. The model, written in CSMP and FSE, simulates daily dry matter production as a function of radiation and temperature, and water and nitrogen availability. Crop aspects of the model are arranged in submodels covering development, photosynthesis, respiration, carbohydrate partitioning, dry matter production, leaf area, grain growth and transpiration. A soil water balance model is attached to simulate water uptake and to determine water stress. Another submodel determines nitrogen uptake, distribution and N stress. Water and nitrogen stresses, depending upon their severity, affect various physiological processes. The model requires inputs relating to site, daily weather, soil physical characteristics and crop management. Switches allow water and/or nitrogen stresses to be terminated to establish climatically determined potential grain yield. Various aspects of the model were validated using a large number of independent experiments. Comparison of simulated and measured quantities indicated satisfactory performance of the model in reference to water and nitrogen uptake, dry matter growth and grain yield in potential as well as Water- and N-limited environments. The model appears useful as a tool for optimizing use of water and nitrogen.